Interpretive Summary: The wood chipping of almond (Prunus dulcis) prunings could provide an alternative to burning that would not contribute to air pollution and add valuable organic matter to soils. The success of wood chipping depends on whether the wood chips delete the soil of critical nutrients necessary for tree growth. An experiment was established where wood chips were mixed with soil and placed in containers, each with an almond tree, in order to quantitatively examine the effect of wood chips on soil nutrients, soil aggregation, and the rhizosphere microbial community. Control trees were planted in containers without wood chips. Tissue analysis was performed on leaf petioles to determine whether the wood chips had an effect on nutrient availability. After the 1st year, trees growing with wood chips had less N, Zn, and Mn while P was increased. After the 2nd year, trees with wood chips no longer had less N levels while P and K were significantly increased, but Zn was decreased. Soil analysis after the 1st year showed significantly higher levels of Ca, Mg, Zn, Cu, P, and K with wood chips. The % carbon, NH4-N, cation-exchange-capacity (CEC), electrical conductivity (EC), and % organic matter (OM) were increased. The soil pH and NO3-N levels were decreased. Similar results were obtained the 2nd year except that Mn and Fe levels were decreased in wood chipped soils while B and Na were increased. The CEC was no longer higher in wood chipped soils. When nematode populations were assayed after the 1st year there were less Criconemella and more Bunonema, Doryleimida, and free-living bacterial and fungal feeding nematodes in wood chipped soils. Similar results were obtained after the 2nd year except that root lesion was reduced in wood chipped soils. More basidiomycetes were counted in wood chipped soils and detected at higher levels with ELISA. Larger soil aggregates were found in wood chipped soils. Undisturbed wood chipped soils had more soil aggregates than disturbed wood chipped soils.

Technical Abstract:
The wood chipping of almond (Prunus dulcis) prunings could provide an alternative to burning that would not contribute to air pollution and add valuable organic matter to soils. The success of wood chipping depends on whether the wood chips delete the soil of critical nutrients necessary for tree growth. An experiment was established where wood chips were mixed with soil and placed in containers, each with an almond tree, in order to quantitatively examine the effect of wood chips on soil nutrients, soil aggregation, and the rhizosphere microbial community. Control trees were planted in containers without wood chips. Tissue analysis was performed on leaf petioles to determine whether the wood chips had an effect on nutrient availability. After the 1st year, trees growing with wood chips had less N, Zn, and Mn while P was increased. After the 2nd year, trees with wood chips no longer had less N levels while P and K were significantly increased, but Zn was decreased. Soil analysis after the 1st year showed significantly higher levels of Ca, Mg, Zn, Cu, P, and K with wood chips. The % carbon, NH4-N, cation-exchange-capacity (CEC), electrical conductivity (EC), and % organic matter (OM) were increased. The soil pH and NO3-N levels were decreased. Similar results were obtained the 2nd year except that Mn and Fe levels were decreased in wood chipped soils while B and Na were increased. The CEC was no longer higher in wood chipped soils. When nematode populations were assayed after the 1st year there were less Criconemella and more Bunonema, Doryleimida, and free-living bacterial and fungal feeding nematodes in wood chipped soils. Similar results were obtained after the 2nd year except that root lesion was reduced in wood chipped soils. More basidiomycetes were counted in wood chipped soils and detected at higher levels with ELISA. Larger soil aggregates were found in wood chipped soils. Undisturbed wood chipped soils had more soil aggregates than disturbed wood chipped soils.